# A ball is dropped from rest and falls vertically downwards through the air, eventually reaching terminal velocity. Describe how the kinetic energy and the gravitational potential energy of the ball change from the moment it is released until it reaches terminal velocity, and explain why the ball's total mechanical energy decreases during this fall.

> Cambridge International IGCSE Physics (0625) — 1.7 Energy, work and power · Describe and Explain · 4 marks

## Mark scheme (4 marks)

1. Kinetic energy increases as the ball falls (and speeds up)
2. Gravitational potential energy decreases as the ball falls (loses height)
3. Some energy is transferred to the surroundings / lost as thermal (heat) energy due to air resistance / friction with the air
4. Total mechanical energy decreases because energy is not conserved within the ball–Earth system / energy is transferred away from the ball by air resistance (so the decrease in GPE is greater than the increase in KE)

## Key terms

- [kinetic energy](https://www.gradenine.co.uk/glossary/kinetic-energy)
- [gravitational potential energy](https://www.gradenine.co.uk/glossary/gravitational-potential-energy)
- [terminal velocity](https://www.gradenine.co.uk/glossary/terminal-velocity)
- [total mechanical energy](https://www.gradenine.co.uk/glossary/total-mechanical-energy)

## Related

- [Revision notes for Cambridge International IGCSE Physics (0625)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-ball-is-dropped-from-rest-e01cae22) · Published by Druglandscape Ltd.